Meaning of cross matching

cross' match"ing

Pronunciation: (krôs'mach", kros'-). [key]
— Med. Med.
  1. the testing for compatibility of a donor's and a recipient's blood prior to transfusion, in which serum of each is mixed with red blood cells of the other and observed for hemagglutination.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.